1. Technical Field
This invention relates to the field of portable personal computers and more particularly to maintaining systems for data security in a portable digital information environment.
2. Description of the Prior Art
The security of personal information has forever been a concern. It has been ensured by locks, codes and secret pockets. As information has taken new forms, new methods have been required to meet the changed situations.
Historically, security of information has been addressed by use of signatures, credentials and photographs. Electronic devices such as automatic banking machines have added encoded cards and personal identification numbers (PINS) to the repertoire of security tools. Computer systems continue to use passwords.
More recently the "Smart Card" has been used as a security tool. The "Smart Card" is a small microcomputer with writable, non-volatile memory and a simple input/output interface, fabricated as a single chip and embedded in a plastic "credit card". It has exterior pads to allow it to be connected to specially designed equipment. The program contained in the card's microcomputer interacts with this equipment and allows its nonvolatile memory data to be read or modified according to the desired algorithm which may optionally include a password exchange. Special techniques have been implemented to protect the memory information and to allow varied permissions according to the situation. For example, U.S. Pat. No. 4,382,279 entitled, "Single Chip Microprocessor with On-Chip Modifiable Memory" discloses an architecture which permits automatic programming of a non-volatile memory which is included on the same chip as a processing and control unit. As in other systems, the microprocessor only protects memory on the same chip.
The "Smart Card" has been used both to facilitate the process of identification and to be the actual site of the valued information. In this situation, as in most past situations, physical presence of a "key" as well as some special knowledge has been used as part of the verification or authentication process. In such above cases, identification has been a dialog between the person desiring access and a fixed agency such as a security guard or an automatic teller machine.
The current state of portability of freestanding computing devices makes it possible for both the physical key and the authentication agent to be small, portable and hence more subject to loss or theft. Further, computing devices make it possible to perform repeated attempts to guess or deduce the special knowledge or password associated with the identification process. This is especially true if the authentication agent or device is also in the control of the thief or burglar. To make matters worse, technology now allows and encourages the carrying of enormous amounts of sensitive information in a pocket or handbag where it is subject to mishap.
Today, notebook and subnotebook sized computers provide a capable freestanding environment which allows for significant computing power and thus creates a need for additional data storage capability. This has initially been met by miniature hard disk devices which hold both programs and data. While password protection is often used in these systems, it does not completely protect sensitive data because, first, the authentication agent is itself vulnerable. However, more significantly, the disk drive containing the data can be physically removed and accessed in a setting more conducive to data analysis. In this case, only some form of encryption is capable of protecting the data. The nature of disk access makes this possible without undue performance or cost barriers. An example of this type of system is described in U.S. Pat. No. 4,985,920 entitled, "Integrated Circuit Card."
The recent emergence of the flash memory and removable "memory cards" has allowed major reductions in size and power requirements of the portable computer. The flash memory combines the flexibility of random access memory (RAM) with the permanence of disks. Today, the coupling of these technologies allows up to 20 million bytes of data to be contained, without need of power, in a credit card size, removable package. This data can be made to appear to a host system either as if it were contained in a conventional disk drive or as if it were an extension of the host's memory. These technological developments have made further reduction in system size possible to the extent that it may be carried in a pocket rather than in a handbag or briefcase.
Thus, the data and its host system have become more vulnerable to loss or theft and simultaneously more difficult to protect memory data by encryption as this presents major cost and performance barriers.
Accordingly, it is a primary object of the invention to provide a portable digital system with a secure memory subsystem.
It is another object of the invention to provide a memory card which can be protected if removed from a portable digital system.
It is still a further object of the present invention to provide a memory card in which the chips of the card are protected if removed from such card.